Introduction to solid state lighting pdf

The transformer can convert the low power control signal from the primary coil to the secondary coil to generate a signal for driving the electronic switch. After processing by rectification, amplification or other modifications, the signal from the secondary coil can be used to drive the switching component. The optical coupler is an opto-isolator that consists of an infrared source usually, a light-emitting diode, or LED and a photo-sensitive semiconductor component such as a photosensitive diode, a photo-sensitive transistor, and a photo-sensitive thyristor.

According to the different components Figure 4. The photo-semiconductor device detects the infra-red radiation from the LED, and then produces a signal to drive the semiconductor switch. Compared with reed relay and transformer, the optical isolator has better physical isolation ability, to ensure the electrical insulation between high voltage output load circuit and low voltage input signal circuit.

And on account of the excellent isolation performance and very compact size of the optocoupler, the optocoupler solid state relay is used in a very wide range of applications.

The input and output circuits of the hybrid solid-state relays are composed of an SSR relay and a reed switcher or a micro-electromagnetic relay in parallel, controlled by different control signals Figure 4. Since the electronic switch has no moving parts, it can switch the load stably and quickly, and does not generate an arc due to high line voltage or heavy surge current during switching. After the load current is generated, the EMR will be controlled by the control signal 2 and switched on.

According to different circuit structure, the solid-state relay can be divided into Discrete Structure Type solid state relays and Hybrid Structure Type solid state relays. The discrete structure solid state relays are mostly assembled by discrete components and printed-circuit board , and then packaged by epoxy resin potting, plastic sealing or resin wrapping.

The hybrid structure solid state relays use thick-film combine technology to assemble discrete components and semiconductor integrated circuits IC , and then encapsulate them in a metal or a ceramic housing. According to the performance, the solid-state relay can be divided into the Standard Type solid state relays , and the Industrial Type solid state relays. The rated current of the standard solid-state relay is generally 10A to A, and the rated current of the industrial solid-state relay is relatively large, can be 60A to A or larger.

Therefore, the industrial SSR relay can meet the strict requirements of the industrial environment and industrial machinery. The plug-in solid-state relays with many package standard like SIP, Mini-SIP, and DIP , can be directly soldered on the printed circuit board, relying on natural cooling, without the need for a heat sink; the flange mounting solid state relays require the additional metal plate or heat sink to dissipate heat.

The latching relay can keep conducting and continuously output the control signal even if cutting off the control current, and it can only be turned off by inputting the reverse current or the off button. The latching is usually used in high-voltage circuits to avoid the expansion of accidents. The basic parameters of solid-state relays fall into three categories: Input Parameters, Output Parameters and Other Parameters.

When the input voltage the voltage applied to the input terminal is greater than or equal to the turn-on voltage, the output terminal will be turned on. When the input voltage the voltage applied to the input terminal is less than or equal to the shutdown voltage, the output terminal will be turned off. Strictly speaking, the zero-crossing voltage is not a voltage point but a voltage range that determined by the internal components of the zero-crossing relay, which is typically very low and almost negligible.

If the power supply voltage is below the zero-crossing voltage, the zero crossing relay will not be turned on; and if the voltage is beyond the zero-crossing voltage, the zero crossing relay will be in the on-state.

This parameter is an indicator of the quality and performance of solid-state relays. The smaller the output voltage drop and the output leakage current, the better the solid-state relay. Inrush current , also known as overload current, input surge current, or switch-on surge current, refers to the non-repetitive maximum or overload current value that the device will not be permanent damage and the output terminals can withstand, when the solid-state relay is in the on-state.

Power Consumption , refers to the maximum power value consumed by the solid-state relay itself in the power-on state and the power-off state. This is also an important parameter to judge the performance of solid-state relays.

The shorter the turn-on time and the turn-off time, the better the switching performance of the solid-state relay. It can also include the measured resistance value between the input terminal and the outer casing including the heat sink , and the measured resistance value between the output terminal and the housing.

It can also include the maximum voltage that can be tolerated between the output terminal and the housing, and the maximum voltage that can be tolerated between the input terminal and the outer casing. In operation, it is usually higher than the case temperature and the external temperature of the component. The maximum junction temperature is the highest junction temperature allowed by the output switching component.

Through this chapter you will learn how do solid state relays work. Because of the different application environments, solid-state relays have slightly different internal components, but the working principle is similar. The internal equivalent circuit diagram of ordinary solid-state relays is shown in the figure below Figure 6.

The principle of solid-state relays can be simply described as: for the NO-SSR, when the appropriate control signal is applied to the Input Terminal IN of the solid-state relay, the Output Terminal OUT will be switched from the off state to the on state; if the control signal is cancelled, the Output Terminal OUT will be restored to the off-state.

In this process, the solid state relays realize non-contact control of switch states of the load power supply which is connected to output terminals. It should be noted that the input terminal can only be connected to the control signal, and the load should only be connected to the output circuit. They are not compatible with each other and cannot be mixed. Since zero-crossing AC solid state relays are completer and more typical than other types of solid state relays, the operation details of AC zero-crossing SSR relays can help illustrate the complete working principle of SSR relays:.

The most commonly used component in the coupling circuit is the optocoupler with high action sensitivity, high response speed, and high dielectric strength withstand voltage between the input and output terminals. Since the input load of the photo-coupler is a light emitting diode LED , this makes the input value of the solid-state relay easy to match the input signal level of the control device, and make it possible to connect the input terminals of the SSR relays directly to the computer output interface, that is, the solid state relay can be controlled by the logic level of "1" and "0".

The function of the Trigger Circuit B is to generate a suitable trigger signal to drive the Switching Circuit D to operate. However, if no special control circuit is added, the switching circuit will generate Radio Frequency Interference RFI , which will pollute the grid by the higher harmonics and the spikes, so the Zero-Crossing Detector Circuit C is specifically designed to solve this problem.

The Snubber Circuit E is designed to prevent spikes and surges from the power supply from causing impacts and disturbances even malfunctions to the switching transistors. Generally, an RC circuit resistor—capacitor circuit, or RC filter or RC network or a non-linear resistor such as varistor is used as the snubber circuit.

The varistor , also called voltage-dependent resistor VDR , is an electronic component whose resistance value varies nonlinearly with the applied voltage, and the most common type of varistor is the metal-oxide varistor MOV , such zinc oxide nonlinear resistor ZNR.

R1 is a current limiting resistor that limits the input signal current and ensures that the optocoupler is not damaged. LED is used to display the input state of the input control signal. The diode VD1 is used to prevent the optocoupler from being damaged when the positive and negative poles of the input signal are inverted. The optocoupler OPT electrically isolates the input and output circuits.

The triode M1 acts as an inverter, and constitute the zero-crossing detection circuit with the thyristor SCR at the same time, and the operating state of the SCR thyristor is determined by the alternating-voltage zero-detection transistor M1. R6 is a shunt resistor used to protect the BCR. R7 and C1 make up a surge absorbing network to absorb spike voltage or surge current in the power mains to prevent shock or interference to the switching circuit.

RT is a thermistor that acts as an overheating protector to prevent solid state relays from being damaged due to excessive temperatures. VDR is a varistor that acts as a voltage-limiting device that clamp the voltage and absorbs excess current to protect the solid-state relay when the output circuit is overvoltage.

The AC zero-crossing solid state relay has the characteristics of being turned on when the voltage crosses zero and being turned off when the load current crosses zero. When the opto-coupler OPT is turned off i. Consequently, the triac BCR is in the off state because there is no trigger pulse on the gate control terminal R6.

When an input control signal applied on the input terminal of the solid-state relay, the phototransistor OPT is turned on i. If the voltage at point A is less than the zero-crossing voltage of M1 i. Through the above process, it can be understood that M1 is used as an AC voltage detector for turning on the solid-state relay when the load voltage crosses zero and turning off the solid state relay when the load current crosses zero.

And on account of the function of the zero-crossing detector, the impact of the load circuit on the load is correspondingly reduced, and the radio frequency interference generated in the control loop is also greatly reduced. Here it need be explained what is the zero crossing. In the alternating current, the zero-crossing is the instantaneous point at which there is no voltage present, that is, the junction between the positive half cycle and the negative half cycle of the AC waveform.

In each cycle of alternating current, there will usually be two zero crossings. And if the power mains switches at the instant point of zero crossing, no electrical interference will be generated. The AC solid-state relay equipped with a zero-crossing control circuit will be in the ON state when the input terminal is connected to the control signal and the output AC voltage crosses zero; conversely, when the control signal is turned off, the SSR be in the OFF state until the next zero crossing.

In addition, it should be pointed out that the zero crossing of solid state relay does not actually mean zero volts of the power supply voltage waveform. Figure 6. And U1 and U2 respectively represents the threshold voltage and the saturation voltage of the switching component. And in this zone, the SSR switch cannot be turned on, even if an input signal is added. In this zone, the SSR is immediately turned on, as soon as the input signal is added, and the output voltage increases as the supply voltage increases.

In this region, the switching element thyristor is in the saturated state. And the output voltage of the solid-state relay will no longer increases with the increase of the power supply voltage, but the current increases with increasing voltage, which can be regarded as an internal short circuit state of the output circuit of the solid-state relay, that is, the solid-state relay is in the Switch-On state as an electronic switch.

And because of the nature of the thyristor, the solid-state relay will be in the on state after the voltage of the output terminals reaching the threshold voltage or the trigger voltage of the trigger circuit. Then the solid-state relay will be in the actual on state after reaching the saturation voltage, and at the same time, generate a very low on-state voltage drop. Through this chapter you will learn where to use solid state relays and what is solid state relay used for.

The fast switching, long life and high reliability of solid-state relays make themselves excellent in the light control system. In the field of traffic lights, the working environment of traffic lights is complicated, but solid-state relays with excellent characteristics moisture proof, explosion-proof, anti-corrosion can face it.

And in stage lighting control systems usually applied to the production of theatre, dance, opera and other performance arts , solid state relays can work with the computer system to control multiple lights, and implement complex lighting effects to increase the atmosphere of the stage. Remote control systems typically require small current signals to control high power equipment, such as electric motors , pulse valves , and other machinery.

As an electronic switching element without mechanical contacts, solid state relays are widely used in remote control systems with excellent advantages: flexible control, high reliability, high durability, no spark, no noise, fast switching, high operating frequency, strong anti-interference ability, etc.

Many traditional mechanical relays in Computer Numerical Control machinery CNC machine are gradually being replaced by the solid-state relays. On account of the excellent durability and high sensitivity abilities, the solid state relays are applied to ensure the high precision and high quality of CNC machining.

In the servo system of CNC machine, the solid state relay can receive the control signal continuously, and control the processing machine accurately. The solid-state relays also perform well in temperature control equipment.

In the field of medical equipment , the equipment has strict requirements of operating frequency and precise operations, so the components of medical equipment should have nice performance high precision, durability, etc. Solid state relays can meet these demands of most medical devices, for example, the infrared radiation devices have a huge thermal inertia, but by connecting the solid-state relays to the radiation plate, it becomes very easy to control the temperature of the infrared radiation device through the solid state relays.

Solid state relays are widely applied in the field of electric vehicles. For example, the explosion-proof solid-state relays are used in the fuel-cell vehicles hydrogen fuel cells to avoid electric arcs and incorrect operation during vibration. As well as, each high-voltage power unit is protected by the combination of multiple solid-state relays, fuses and filter capacitors.

Considering the complex working conditions and special requirements the explosion-proof, moisture-proof and anti-corrosion abilities of the chemical and mining industry , the traditional mechanical relays cannot meet such requirements, therefore lots of solid-state relays are used to the intermediate controllers of the major mechanical equipment, such as the solid state relays equipped in large coal mining elevators.

The computer control system including the computer peripheral devices have high requirements of relays, but types various of solid-state relays can help the computer devices control assorted power units to drive the large mechanical automation equipment, or hydraulic and pneumatic equipment, because solid state relays have the characteristics: zeroing-crossing, nice electromagnetic compatibility, high sensitivity, fast switching speed, low level control signals, compatible with logic circuit TTL, CMOS, DTL, HTL and even can be directly connected to the micro-computer control device, and so on.

Office Equipment -- Printer , Shredder Medical Device -- Ultrasonic Oscillator , Autoclave The following are options to consider when selecting the appropriate solid-state relays based on the actual requirements:. Secondly, the voltage of the load power supply should be considered which cannot be larger than the output rating voltage, and less than the minimum voltage of the solid-state relay.

Then consider the magnitude of the load voltage and the transient voltage. The load voltage refers to the steady-state voltage applied to the SSR switch output terminal, and the transient voltage refers to the maximum voltage that the output terminals of the SSR relays can withstand.

When the AC inductive load, single-phase motor load or three-phase motor load is switched or energized, the voltage at the SSR switch output may be twice the peak voltage of the power supply, and this voltage cannot be greater than the transient voltage of the SSR to prevent the excessive shock voltage from damaging the electronic switch. It is recommended to select solid state relays with a varistor absorption circuit and an RC snubber circuit.

The RC circuit blocks certain frequencies from passing and allows other frequency signals to pass to filter out the interfering signals. The output current value of the solid state relay is the steady-state current flowing through the output terminals of SSR, which is usually equal to the current of the load connected to the SSR output terminal. Since the switching elements of the SSR switches are very sensitive to temperature, and the overcurrent can generate a high amount of heat, so the overload capability of the SSR is weak.

The output current requires a margin to avoid excessive inrush currents that reduce the life of the solid-state relay. Besides, the fast fuse and the air switch could be considered to protect the output loop, or add an RC sink loop and a varistor MOV to the output of the relay. Almost all the controlled loads will generate large inrush currents at the moment of turn-on.

For example:. They are purely resistive loads with a positive stability coefficient, but the resistance is small at a low temperature, so the current at startup will exceed several times the steady state current. The locked-rotor is a situation in which the motor still outputs torque when the speed is 0 rpm, at the meantime, the power factor of the motor will be extremely low, and the current can be up to 7 times of the rated current.

Excessive inrush current can damage the semiconductor switches inside the SSR. Therefore, when selecting a relay, the surge characteristics of the controlled load should be analyzed first, so that the relay can withstand the inrush current while ensuring steady-state operation.

The rated current of solid state relay should be selected according to the derating factor in actual requirements. And if the selected relay needs to work in a place with frequent operation, long life and high reliability, the rated current should be divided by 0.

Additionally, the resistor or inductor can be connected in series to the output loop to further limit the current. Attention: Please do not use the SSR surge current value as the basis for selecting the load starting current.

Because the SSR relay surge current value is based on the surge current of electronic switch with the precondition of half or one power supply cycle, that is 10ms or 20ms. There is no pure inductive load and pure capacitive load in the usual electrical appliances, because these two type loads don not do active power. In the series-parallel circuit, if the capacitive reactance is larger than the inductive reactance, the circuit is capacitive load; and vice versa.

In a nutshell, a load that operates only by then resistor-type components is called the resistive load. This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site.

Start by pressing the button below! Author: Arturas Zukauskas Michael S. Shur Remis Gaska. Read more. Light: Science and Magic. An Introduction to Photographic Lighting. Solar Lighting. Interior lighting. Garden lighting. The design of lighting. Lighting efficiency applications. Photographic Lighting Simplified. LightWave v9 lighting.